TIVA

Question 1

what is a TIVA?

Answer 1

anesthesia including IV agents only (pure TIVA)

*may be combined with N2O and regional

Question 2

what is the ideal TIVA drug?

Answer 2

ketamine, covers everything (dissociative, analgesic)

*ketamine and propofol combined are good since they offset the cons of each other

Question 3

what are advantages of TIVA?

Answer 3

• smooth induction with minimal coughing, hiccoughing
• easier control of anesthetic depth
• rapid, predictable emergence with minimal hangover
• decreased incidence of emergence delirium (sevo/iso very insoluble, wake up FAST)
• lower incidence of PONV
• non triggering for malignant hyperthermia (Succs and volatile agents biggest triggers)
• ideal for neurosurgery
• absence of organ toxicity
• absence of atmospheric pollution
• avoids side effects of N2O
• autoregulation of cerebral blood flow maintained
• decreased bleeding in surgical field
• improved mucociliary transport

Question 4

what are disadvantages of TIVA?

Answer 4

• increased post op analgesic demands and cost
• decrease in FVC after operation greater than BAL with sevo
• cost
• no effect on emergence delirium, but less analgesics required and decreased PONV

Question 5

what are indications for TIVA?

Answer 5

• malignant hyperthermia susceptible (hx or family hx)
• cystic fibrosis (mucus makes induction and emergence long for volatiles)
• airway endoscopies, laryngeal and tracheal surgery (rigid airways cause to pollute room)
• remote locations, during transportation
• intracranial HTN (IV anes. agents cerebral vasoconstrictors; decrease CBF, ICP, and CMRO2 opposed to volatiles that cerebral vasodilate)
• craniotomy (rapid awakening for neuro checks)

Question 6

compare continuous infusion technique vs. intermittent bolus for TIVA

Answer 6

continuous infusions

• minimize swings in levels of drugs seen with bolus
• can reduce total drug requirement by 25-30%
• fewer side effects
• shorter recovery times
• decreased drug costs
• provide stable depth of anesthesia

bolus

• injected quickly
• rapid onset of unconsciousness
• side effects of decreased BP and apnea

Question 7

describe propofol

Answer 7

• rapid onset
• pain on injection (use lidocaine)
• myocardial effect (don’t use with hypovolemia)
• apnea (25-30%; even higher with opioids)
• induction dose reduced with versed, opioids
• no accumulation (unlike Thiopental) and early restoration of cognitive and psychomotor function
• reduction in PONV

Question 8

describe ketamine

Answer 8

• only IV anesthetic that can be used as the sole agent for TIVA
• hypnosis, analgesia, amnesia
• sympathetic stimulation (good for trauma and hypovolemia UNLESS catecholamines diminished then returns to baseline depressant)
• HTN, tachycardia, increased ICP, psychologic reactions (no CAD, pulm HTN, neuro; pre treat with versed)
• good for pulmonary disorders (asthma) and congenital heart babies
• discontinue 30 min prior to emergence (allow dissociative effect to wear off)
• increase PONV (unless with propofol)
• unpleasant hallucinations (pre treat with versed; combine with propofol)
• salivation (pre treat with glycopyrrolate)

Question 9

describe ketamine and propofol combined

Answer 9

• offsets hemodynamic effects
• offsets respiratory effects to maintain spontaneous vent
• propofol offsets PONV and hallucinations

Question 10

how should dosing be mixed with propofol and ketamine?

Answer 10

• mix ketamine with 2mg/ml of propofol
• induce with 1-2 mg/kg of propofol in mixture
• give an additional 0.5-1 mg/kg of ketamine after LOC
• infuse 140-200 mcg/kg/min first 10 mins
• 100-140 mcg/kg/min for next 2 hours
• 80-120 mcg/kg/min after 2 hours
• rate based on propofol

Question 11

describe remifentanil

Answer 11

• rapid onset, potency 5x fentanyl
• allows high dose opioids w/o delayed recovery, no matter length of infusion time
• titrates easily
• increased shivering and post op pain (give analgesic before stopping)
• less time to emergence and less PONV
• good for craniotomies for rapid awakening (post op pain, give analgesic in time before stopping) and carotid endarterectomy (no post op pain; rapid awakening)

Question 12

describe maintenance of remifentanil infusion

Answer 12

• turn on a 1 mcg/kg/min
• never bolus (stiff chest; metabolized too quickly)
• maintain at 0.1-0.4 mcg/kg/min
• metabolized rapidly by plasma esterases
• turn off 5-7 min before extubation
• start post op analgesia prior to discontinuing remifentanil (recovery 3-5 min SV)

Question 13

describe dexmedetomidine

Answer 13

• used in sedation (not general)
• anxiolysis and analgesia (no loss of consciousness)
• prolonged recovery r/t higher doses required for anesthesia (compared to propofol) *good if planned to be post of ventilated
• reduced need for opioids
• decreased PONV

Question 14

what is the most reliable sign of inadequate anesthesia?

Answer 14

movement

Question 15

describe titration goals

Answer 15

• maintain 1-2 twitches of ToF to allow movement (weak but to see awareness)
• bispectral index (frontal EEG)
• anticipate increased requirement during intubation and skin incision
• anticipate decreased requirement during prep and drape

Question 16

describe method of titration

Answer 16

• if no response for 10-15 min, the infusion rate may be reduced about 20%
• watch for movement, changes in hemodynamics to determine need to titrate
• if pt. responds, administer bolus, and increase rate to a point b/w first and second rate
• except for remifentanil, don’t titrate opioids
• titrate down to allow SV at the end of surgery (slowly since surgeon still working)

Question 17

what is the context sensitive half time of propofol?

Answer 17

• up to 3 hours: 10 min
• after 3 hours: 25 min
• after 8 hours: 40 min

Question 18

what is the context sensitive half time of ketamine?

Answer 18

after 8 hours: 50 min

Question 19

what is the CSHT of remifentanil?

Answer 19

4 min after any duration

Question 20

what is the CSHT of sufentanil?

Answer 20

after 4 hours: 30 min

Question 21

describe target controlled infusion systems

Answer 21

• programs pts. weight, height, age
• based on a pharmacokinetic model which describes the elimination and redistribution of the drug
• can titrate predicted blood concentration of the drug as simply as volatile agents for varying levels of surgical stimulation and individual pt. requirements